In recent years, the availability and quality of colour reproduction systems, such as colour laser copiers, coloured ink jet printers and colour offset printers has increased dramatically. As a result of these increases in availability and quality, the incidence of forgeries being produced on such devices has also increased dramatically. Obviously, an increased incidence of forgeries is of great concern to the general fabric of society. Social concerns have risen to such an extent that the relevant authorities of various governments have seriously considered restricting or banning the use of these devices because of concerns over the increased levels of forgery.
These is therefore a general need for an inexpensive form of device that can detect when a document of value is being copied or printed and be able to disable the printing device so as to discourage its use in the production of forgeries.